The invention relates to a method and a device for compressing a gas-phase medium, particularly hydrogen or natural gas, wherein the medium may have a water content as high as complete saturation with water and wherein the medium is compressed in a single or multiple stages in at least one liquid-filled chamber.
A species-related method and species-related device for compressing a gas-phase medium are known from German patent application 102004046316. In methods and devices of such kind, the gas-phase medium is compressed in a liquid column. Ionic liquids in particular have proven to be useful as liquids in such columns, because they do not mix with the medium that is being compressed and can be separated from the compressed medium without residue. Species-related methods are also used for compressed any gas-phase media that have been or are contaminated with water as a consequence of their production, processing or their natural occurrence.
Ionic liquids are low melting, organic salts with melting points between 100 and 90° C., and most known ionic liquids are already in the liquid state at room temperature. Unlike conventional molecular liquids, ionic liquids are entirely ionic and accordingly they possess new and unusual properties. The properties of ionic liquids can be adapted fairly readily to existing technical problems by varying the structure of the anion and/or cation and by varying their combinations. Unlike conventional, molecular liquids, ionic liquids also have the advantage that they do not have any measurable vapor pressure. This means that not even the slightest traces evaporate—even in a high vacuum—until their decomposition temperature is reached. This is the aspect that is behind their other properties of nonflammability and environmental compatibility, because ionic liquids thus cannot escape into the atmosphere, Moreover, ionic liquids are very thermostable. The decomposition points of most are above 400° C. Density and mixing behavior with other liquids can be modified or adjusted for most ionic liquids by appropriate selection of the ions. Ionic liquids also have the further advantage that they are electrically conductive, so that accordingly they can prevent the buildup of electrical charges—which present potential hazard,
Species-related methods and devices are used particularly for compressing gas-phase hydrogen or natural gas. In this context, until now the problem that has presented itself has been that the hydrogen to be compressed inevitably contains water by virtue of the method of its production—by electrolysis for example. Previously, this had to be removed completely before proceeding with the actual compression, because it must not be allowed to come into contact with the previously known ionic liquids, since it would attack and destroy them. For this reason, until now it has been necessary to provide fairly complicated devices or systems for separating the water. In the case of oxygen production by electrolysis, for example, molecular sieves are used. However, these need energy because they have to be heated cyclically, and they also consume a portion of the valuable hydrogen, which is used as the purge gas for regenerating the molecular sieve. The necessary separation of the water thus makes hydrogen generation more expensive. Furthermore, devices of such kind require a certain degree of maintenance, which further raises the cost of generating hydrogen. The same problems are also encountered when compressing other media, such as natural gas for example, which must be compressed for use in refueling vehicles.